The invention relates to a rotary sprayer for spraying coating material, to a coating installation including such a sprayer, and also to a method of verifying the operating state of such a sprayer.
In an installation for spraying coating material, it is known to atomize the material by means of a rotary element, referred to as a bowl or cup, that is fed with the material and that rotates at a speed usually lying in the range 2000 revolutions per minute (rpm) to 120,000 rpm. At the speeds under consideration, the bowl must be as light as possible and balanced so as to avoid unbalance as much as possible, particularly if its rotary drive means include a turbine with an air bearing.
It is known, for example from WO-A-94/12286, to connect a bowl to a rotor by means of an engagement ring capable of expanding radially. It is also known, e.g. from WO-A-01/62396, to use magnetic coupling means between the bowl and the rotor of a turbine.
In a rotary sprayer provided with an air bearing, and as provided in EP-A-0 567 436, it is possible to use a microphone to obtain an indication concerning the speed of rotation of the rotary portion. Such a microphone delivers a signal even if the rotary portion is not fitted with a bowl or if the bowl is poorly mounted.
With known equipment, there exists a risk of starting the sprayer while it is not fitted with the bowl or while the mounting of the bowl relative to its drive rotor has not been performed correctly. Starting a sprayer without the bowl can lead to certain portions of the sprayer becoming polluted and also to coating material being deposited in unsuitable manner on one or more articles to be coated, which can require them to be rejected. With an electrostatic sprayer, putting voltage unit without the coating material being atomized by the bowl can lead to an electric arc being formed between a continuous jet of non-atomized coating material and an article at ground potential, and that can be dangerous. When a bowl is poorly mounted on its drive member, it is liable to become detached therefrom suddenly, because of the accelerations to which it is subjected, being ejected therefrom violently, which can be dangerous for personnel present on site, and which can result in articles to be coated or certain portions of the installation being damaged.
The invention seeks particularly to remedy those drawbacks by proposing a rotary sprayer of operation that is made more reliable than sprayers in the state of the art.